1. Field of the Invention
The present invention relates to a balloon for an intraocular lens and processes for its production. More particularly, it relates to a balloon useful as an intraocular lens to be used as a lens for correcting the eyesight or vision after the surgery to remove a cataract and capable of being inserted through a small incision and being snugly fit and held in a lens capsule, and advantageous processes for its production.
2. Discussion of the Background
With respect to intraocular lenses useful as lenses for correcting the eyesight or vision after the surgery to remove cataracts, there has been an increase in their use under a number of clinical tests along with improvements of the lenses and progress of the surgical techniques in recent years. It has been recognized that they are functionally far superior to eye glasses or contact lenses for aphakias, which used to be commonly employed.
Such intraocular lenses are generally classified into anterior chamber lenses, iris-supported lenses and posterior chamber lenses depending upon the sites for implantation. Among them, a posterior chamber lens implanted at the position for the crystalline lens is preferred. It is particularly preferred to implant it in the capsule of the posterior chamber, since such is most natural.
To implant such an intraocular lens in the lens capsule, it is necessary to incise the sclera of the eye for the insertion of the lens into the capsule, and such an incision is required to be sufficiently large for the insertion of the lens therethrough. However, if the incision is large, astigmatism is likely to result after the surgery. Accordingly, it is desired that an intraocular lens to be inserted is capable of being inserted through a small incision.
For this purpose, some proposals have been made for intraocular lenses to be inserted and fixed in lens capsules. For example, U.S. Pat. No. 4,449,257 proposes to use a swellable lens made of a water-absorptive hydroxyethyl methacrylate polymer and to insert it in a small dried state and let it expand with the uptake of aqueous humor in the eye to form a soft lens. However, with an intraocular lens of such a structure, the incision of the sclera can not be reduced beyond a level of about 4 mm when it is made of a hydroxyethyl methacrylate polymer, although it depends on the swellability of the material.
Further, since an intraocular lens is to be implanted in the lens capsule for a crystalline lens, it is required to have elasticity to follow the movememt of the crystalline lens. It is further desired to have the same shape as the crystalline lens and to be capable of being intimately fit in the lens capsule for the crystalline lens. However, such an intraocular lens has not yet been developed, and its production has been very difficult.
Under these circumstances, it is an object of the present invention to form an intraocular lens to be inserted and fixed in the lens capsule in the form of a hollow balloon having substantially the same shape as the crystalline lens so that it is capable of being snugly fit and held in the lens capsule and capable of being inserted even through a smaller incision than ever to solve the problem of the size of the incision.
Another object of the present invention is to provide processes for advantageously producing such a balloon for an intraocular lens.
The present invention provides a balloon for an intraocular lens, which is a unitary elastic hollow body made of an elastomer and having a convex lenticular shape without projections along its circumference, which gives, when inserted in a lens capsule, a configuration corresponding substantially to the shape of the lens capsule, said hollow body having a wall thickness of from 0.001 to 0.1 mm at its optical portion and a diameter of from 6 to 13 mm, and capable of being inflated in the lens capsule to form an intraocular lens when a light transmitting injection material is injected into the hollow body.
The present invention also provides a process for producing such a balloon for an intraocular lens, which comprises:
a step of preparing mold halves having mold cavities corresponding respectively to halves of a hollow balloon made of an elastomer and having a convex lenticular shape, and having such balloon halves accommodated in the respective mold cavities; PA1 a step of placing a predetermined amount of an adhesive monomer in one or each of the balloon halves, and closing the mold halves having the balloon halves accommodated therein so that the convex side of each balloon half is located outside and the peripheral edges of the balloon halves abut against each other; and PA1 a step of polymerizing the adhesive monomer while rotating the closed mold about an axis through the centers of the balloon halves, so that the abutting peripheral edges of the balloon halves are bonded by the polymer of the adhesive monomer. PA1 a step of preparing a first mold half having a mold cavity corresponding to a half of a hollow balloon made of an elastomer and having a convex lenticular shape, and having such a balloon half accommodated in the mold cavity; PA1 a step of preparing a second mold half having a mold cavity corresponding to the other half of the hollow balloon, and closing the first and second mold halves with a predetermined amount of a balloon-forming monomer polymerizable to form an elastomer placed therein; and PA1 a step of polymerizing the monomer while rotating the closed mold about an axis through the center of the balloon half, so that the other half of the hollow balloon is formed in the second mold half and at the same time, the other balloon half is integrally bonded to the balloon half accommodated in the first mold half along the peripheral edge of the latter balloon half. PA1 a step of introducing a predetermined amount of a balloon-forming monomer polymerizable to form an elastomer into each of mold halves for halves of a hollow balloon having a convex lenticular shape, and casting the monomer on the surface of each mold; PA1 a step of closing the mold halves with the cast monomer accommodated therein; and PA1 a step of polymerizing the monomer while rotating the closed mold, so that balloon halves are formed in the respective mold halves, and at the same time, the peripheral edges of the balloon halves are bonded to each other. PA1 a step of introducing a predetermined amount of a balloon-forming monomer polymerizable to form an elastomer into a first mold half for a half of a hollow balloon having a convex lenticular shape, and casting the monomer on the surface of the first mold half; PA1 a step of introducing a predetermined amount of a balloon-forming monomer polymerizable to form an elastomer into a second mold half for the other half of the hollow balloon, and overlaying the first mold half on the second mold half to close the mold halves; and PA1 a step of polymerizing the monomers while rotating the closed mold, so that balloon halves are formed in the respective mold halves, and at the same time, the peripheral edges of the balloon halves are bonded to each other.
The present invention provides another process for the production of such a balloon, which comprises:
The present invention provides a further process for the production of such a balloon, which comprises:
The present invention provides a still another process for the production of such a balloon, which comprises: